Optical imaging device with thermal attenuation

ABSTRACT

An optical imaging device, in particular for use in microlithography, includes a mask device for receiving a mask having a projection pattern, a projection device with an optical element group, a substrate device for receiving a substrate and an immersion zone. The optical element group is adapted to project the projection pattern onto the substrate and includes a plurality of optical elements with an immersion element to which the substrate is at least temporarily located adjacent to during operation. During operation, the immersion zone is located between the immersion element and the substrate and is at least temporarily filled with an immersion medium. A thermal attenuation device is provided, the thermal attenuation device being adapted to reduce fluctuations within the temperature distribution of the immersion element induced by the immersion medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toU.S. application Ser. No. 12/267,074, filed Nov. 7, 2008, which is acontinuation of International Application No. PCT/EP2007/054503, filedon May 9, 2007, which claims priority to German Application No. 10 2006021 797.7, filed May 9, 2006. U.S. application Ser. No. 12/267,074 andInternation application PCT/EP2007/054503 are incorporated herein byreference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to an optical imaging device. Disclosedembodiments may be used in the context of microlithography used infabricating microelectronic circuits. The disclosure further relates toan optical imaging method which may, among others, be performed with theoptical imaging device.

BACKGROUND

In microlithography it is generally desirable to keep the position andthe geometry of the components (e.g., the optical elements such aslenses, mirrors and gratings) of an imaging device unchanged duringoperation to the highest possible extent in order to achieve acorrespondingly high imaging quality. The tough requirements withrespect to accuracy lying in a microscopic range in the area of a fewnanometers are none the less a consequence of the permanent need toreduce the resolution of the optical systems used in fabricatingmicroelectronic circuitry in order to push forward miniaturization ofthe microelectronic circuitry to be produced.

In order to achieve an increased resolution either the wavelength oflight used may be reduced as it is the case with systems working in theextreme ultraviolet (EUV) range at working wavelengths in the area of 13nm or the numerical aperture of the projection system used may beincreased. One possibility to remarkably increase the numerical apertureabove the value 1 is realized in so-called immersion systems, wherein animmersion medium having a refractive index larger than 1 is placedbetween an immersion element of the projection system and the substrateto be exposed. A further increase in the numerical aperture is possiblewith optical elements having a particularly high refractive index.

In a so-called single immersion system, the immersion element (i.e. theoptical element at least in part contacting the immersion medium in theimmersed state) typically is the last optical element located closest tothe substrate to be exposed. Here, the immersion medium typicallycontacts this last optical element and the substrate. In a so-calleddouble immersion system, the immersion element does not necessarily haveto be the last optical element, i.e., the optical element locatedclosest to the substrate. In such double or multiple immersion systems,and immersion element may also be separated from the substrate by one ormore further optical elements. In this case, the immersion medium theimmersion element is at least partly immersed in may be placed, forexample, between two optical elements of the optical system.

With the reduction of the working wavelength as well as with theincrease of the numerical aperture not only the requirements withrespect to the positioning accuracy and the dimensional accuracy of theoptical elements used become more strict throughout the entireoperation. Of course, the requirements with respect to the minimizationof imaging errors of the entire optical arrangement increase as well.

The temperature distribution within the optical elements used and thedeformation of the respective optical element eventually resulting fromthe temperature distribution as well as an eventual temperature relatedvariation of the refractive index of the respective optical element canbe important in this context.

Various approaches taken to actively counteract heating of a mirror(e.g., in an EUV system) resulting from the incident light and to keep atemperature captured at a given location within the mirror activelywithin given limits. For example., one can use a temperature adjustmentdevice located centrally on the backside of a mirror including Peltierelements or the like to provide targeted cooling. This solution, on theone hand, can have the disadvantage that it is not suitable for use withrefractive optical elements as they are used in particular with theimmersion systems mentioned above since the central temperatureadjustment device would then cover the area optically used. On the otherhand, only the temperature of a single location within the mirror isgenerally reliably controlled in a more or less stationary stateconsidering the light energy absorbed by the mirror. Further thermalinfluences of the environment, in particular non-stationary and/orlocally varying thermal influences as they may be introduced by animmersion medium and as they may cause dynamic and local fluctuations inthe temperature distribution within the mirror, respectively, remainunconsidered. See, e.g., EP 1 477 853 A2 (to Sakamoto), the entiredisclosure of which is incorporated herein by reference.

SUMMARY

In general, in one aspect, the disclosure features an optical imagingdevice as well as an optical imaging method not showing thesedisadvantages or at least showing them to a lesser degree and, inparticular, allows in a simple manner compensation of local thermalenvironmental influences to the optical element besides theconsideration of absorption effects of the projection light.

It is believed that such thermal environmental influences, inparticular, influences originating from the immersion medium, in animmersion system may cause local fluctuations within the temperaturedistribution of the respective optical elements that are not negligibleor even considerable in relation to the absorption effects of theprojection light. Accordingly, it is believed that the desiredcompensation of such thermal environmental influences can also bepossible with refractive systems and refractive optical elements,respectively, as they are used with immersion systems if a correspondingthermal attenuation is available reducing, besides the absorptionrelated fluctuations, also fluctuations in the temperature distributionof the respective optical element induced by the environment of therespective optical element. To this end, with a variant with animmersion system, a thermal attenuation device can be provided for animmersion element, the thermal attenuation device being adapted toprovide a reduction of fluctuations in the temperature distribution ofthe immersion element induced by the immersion medium. It is possible,besides accounting for absorption effects, to account for the localfluctuations within the temperature distribution of the immersionelement in induced, among others, by the immersion medium.

In some embodiments, in particular for refractive elements, acorresponding temperature behavior model, in particular accounting fornon-stationary and/or local environmental influences, may be set up andused in an active control of the temperature distribution. With such atemperature behavior model, one can predict or estimate the temperaturedistribution which is, if at all, only hardly to the measured in theoptically used area without disturbance to the imaging process, and toaccount for this predicted or estimated temperature distribution in thecontrol of the temperature distribution.

In a further aspect, the disclosure features an optical imaging device,in particular for use in microlithography, including a mask device forreceiving a mask comprising a projection pattern, a projection devicewith an optical element group, a substrate device for receiving asubstrate and an immersion zone. The optical element group is adapted toproject the projection pattern onto the substrate and includes aplurality of optical elements with an immersion element to which thesubstrate is at least temporarily located adjacent to during operation.During operation, the immersion zone is located between the immersionelement and the substrate and is at least temporarily filled with animmersion medium. A thermal attenuation device is provided, the thermalattenuation device being adapted to reduce fluctuations within thetemperature distribution TE of the immersion element induced by theimmersion medium.

In another aspect, the disclosure features an optical imaging method, inparticular for use in microlithography, wherein a projection pattern isprojected onto a substrate using the optical elements of an opticalelement group, an immersion element of the optical element group beingat least partly immersed in an immersion medium in the area of animmersion zone located adjacent to the substrate. According to thedisclosure, via a thermal attenuation device, fluctuations in thetemperature distribution TE of the immersion element induced by theimmersion medium are reduced.

In another aspect, the disclosure features an optical imaging device, inparticular for microlithography, comprising a mask device for receivinga mask comprising a projection pattern, a projection device with anoptical element group, a substrate device for receiving a substrate andan immersion zone, wherein the optical element group is adapted toproject the projection pattern onto the substrate. The optical elementgroup includes a plurality of optical elements with at least oneimmersion element at least temporarily immersed in an immersion mediumin the area of an immersion zone during operation. There is provided athermal attenuation device adapted to reduce fluctuations within thetemperature distribution TE of the immersion element induced by theimmersion medium, wherein the thermal attenuation device includes atleast one thermal decoupling device for at least partial thermaldecoupling of the immersion element from at least a part of itsenvironment.

In another aspect, the disclosure features an optical imaging method, inparticular for use in microlithography, wherein a projection pattern isprojected onto a substrate using the optical elements of an opticalelement group, an immersion element of the optical element group beingat least partly immersed in an immersion medium in the area of animmersion zone. According to the disclosure, via a thermal attenuationdevice, fluctuations in the temperature distribution TE of the immersionelement induced by the immersion medium are reduced, wherein by thethermal attenuation device that at least partial thermal decoupling ofthe immersion element from at least a part of its environment isprovided.

In a further aspect, the disclosure features an optical imaging device,in particular for use in microlithography, comprising a mask device forreceiving a mask comprising a projection pattern, a projection devicewith an optical element group, a substrate device for receiving asubstrate. The optical element group is adapted to project theprojection pattern onto the substrate and includes a plurality ofoptical elements with at least one thermally controlled optical element.According to the disclosure a thermal attenuation device is associatedto the thermally controlled optical element, the thermal attenuationdevice being adapted to reduce fluctuations within the temperaturedistribution TE of the thermally controlled optical element, wherein thethermal attenuation device, for reducing temperature fluctuations withinthe thermally controlled optical element, accesses a temperaturebehavior model of the thermally controlled optical element.

In another aspect, the disclosure features an optical imaging method, inparticular for use in microlithography, wherein a projection pattern isprojected onto a substrate using the optical elements of an opticalelement group, the optical elements comprising a thermally controlledoptical element. According to the disclosure, via a thermal attenuationdevice, fluctuations within the temperature distribution TE of thethermally controlled optical element are reduced, wherein for reducingthe temperature fluctuations within the thermally controlled opticalelement a temperature behavior model of the thermally controlled opticalelement is accessed.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an embodiment of an opticalimaging device according to the disclosure with which an embodiment ofan optical imaging method;

FIG. 2 is a schematic partially sectional view of a part of the imagingdevice of FIG. 1;

FIG. 3 is a schematic partially sectional view showing the detail D ofFIG. 2 for an an embodiment of the optical imaging device;

FIG. 4 is a schematic partially sectional view showing the detail D ofFIG. 2 for an an embodiment of the optical imaging device;

FIG. 5 is a schematic partially sectional view showing the detail D ofFIG. 2 for an embodiment of the optical imaging device;

FIG. 6 is a schematic partially sectional view showing the detail D ofFIG. 2 for an embodiment of the optical imaging device;

FIG. 7 is a schematic partially sectional view showing the detail D ofFIG. 2 for an embodiment of the optical imaging device;

FIG. 8 is a schematic partially sectional view showing the detail D ofFIG. 2 for an embodiment of the optical imaging device;

FIG. 9 is a block diagram of an embodiment of the optical imaging methodwhich may be executed with the optical imaging device of FIG. 1;

FIG. 10 is a schematic partially sectional view of an embodiment of theoptical imaging device.

DETAILED DESCRIPTION

In the following, an embodiment of the optical imaging device for use ina microlithography process will be described with reference to FIGS. 1to 9.

FIG. 1 shows a schematic representation of an embodiment of the opticalimaging device in the form of a microlithography device 101 operatingwith light in the UV range at a wavelength of 193 nm.

The microlithography device 101 includes an illumination system 102, amask device in the form of a mask table 103, and optical projectionsystem in the form of an objective 104 having an optical axis 104.1 anda substrate device in the form of a wafer table 105. The illuminationsystem 102 illuminates a mask 103.1 arranged on the mask table 103 witha projection light beam—not shown in further detail—having a wavelengthof 193 nm. A projection pattern is formed on the mask 104.3 which isprojected with the projection light beam via the optical elementsarranged within the objective 104 onto a substrate in the form of awafer 105.1 arranged on the wafer table 105.

The objective 104 includes an optical element group 106 formed by a gayseries of optical elements 107 to 109. The optical elements 107 to 109are held within the housing 104.2 of the objective. Due to the workingwavelength of 193 nm the optical elements 107 to 109 are refractiveoptical elements such as lenses or the like. Thereby, the last opticalelement 109 located closest to the wafer 105.1 during operation is a socalled closing element or last lens element.

The microlithography device 101 is an immersion system. In an immersionzone 110, a liquid immersion medium 110.1, for example highly purifiedwater or the like, is arranged between the wafer 105.1 and the last lenselement 109. Within the immersion zone 110 there is provided animmersion bath of the immersion medium 110.1 on the one hand downwardlydelimited at least by the part of the wafer 105.1 to be actuallyexposed. The lateral limitation on the immersion bath is provided atleast partially by an immersion frame 110.2 (typically also called animmersion hood). At least the part of the last lens element 109optically used during exposure and the part of the last lens element 109lying on the outer side of the objective 104 is immersed in theimmersion bath such that the last lens element 109 is an immersionelement. Thus, the path of exiting from the last lens element 109between the last lens element 109 and the wafer is located exclusivelywithin the immersion medium 110.

Due to the refractive index of the immersion medium lying above thevalue 1 a numerical aperture NA>1 is achieved and the resolution isenhanced with respect to a conventional system with a gas atmospherebetween the last lens element and the wafer.

In order to achieve a numerical aperture with a value NA>1.4 a materialcan be used for last lens element 109 that has a refractive index abovethe refractive index of quartz (SiO) or calcium fluoride (CaF) typicallyused for such lens elements. In the present embodiment the material ofthe last lens element 109 is a spinel. However, in some embodiments,other lens materials having a correspondingly high refractive index andbeing suitable for the respective wavelength may be used. An example forsuch a lens material is LuAG (Lutetium aluminum garnet, for exampleLu₃Al₅O₁₂). Furthermore, conventional quartz or calcium fluoride lensescan be used. Furthermore, other numerical apertures may be selected.With respect to a high resolution, however, the numerical aperture canhave a value of at least 1.3.

The spinel used for the last lens element 109 is a considerably highertemperature sensitivity of the refractive index than conventional quartzor calcium fluoride lenses. Thus, it is necessary to keep the actualtemperature distribution TE within the last lens element within narrowvariation limits during operation in order to maintain a given setpointtemperature distribution TSE in order to at least reduce (e.g.,minimize) imaging errors resulting from corresponding variations in therefractive index of the last lens element 109.

It will be appreciated however that, in particular in the area ofmicrolithography, with systems having optical elements made from quartz(SiO) or calcium fluoride (CaF), variations or fluctuations in thetemperature distribution of the immersion elements may occur that arenot negligible any more such that, for such systems as well, using thedisclosed techniques for thermal attenuation can be of great advantage.

In order to meet these narrow variation limits around a given setpointtemperature distribution TSE, a thermal attenuation device 111 isprovided. In the following the thermal attenuation device 111 isdescribed in further detail mainly with reference to the FIGS. 2 to 9.FIG. 2 shows—partially in a highly schematic manner—a half-section ofthe wafer side end of the objective 104.

In the present example, thanks to the thermal attenuation device 110, amaximum deviation ΔTE=1 mK from a given setpoint temperaturedistribution TSE of the last lens element 109 is achieved duringoperation of the microlithography device 101. the imaging errors andimaging error variations, respectively, resulting from family induceddeformation and thermally induced refractive index alterations may bekept sufficiently low in order to achieve a high imaging quality.However, it will be appreciated that, with other variants of thedisclosure, other, eventually higher maximum deviations are possible, inparticular depending on the thermal deformation behavior and the thermalrefractive index variation of the material used. In some embodiments,these maximum deviations do not exceed 10 mK since then a particularlyhigh imaging quality may be achieved.

It will be appreciated in this context that the given setpointtemperature distribution TSE may be arbitrarily selected. It may beselected such that the last lens element 109 in itself, at least oneimaging error type, has a minimized imaging error. However, it may alsobe selected such that the last lens element 109, at this setpointtemperature distribution TSE, in itself for at least one imaging errortype has an imaging error having a sufficient amount to reduce or evenfully compensate a corresponding imaging error of the remaining opticalelements of the optical element group 106 such that at least one imagingerror type the overall imaging error of the objective 104 is minimized.See, e.g., EP 0 956 871 A1 (to Rupp), the entire disclosure of which isincorporated herein by reference.

The thermal attenuation device 111 includes a plurality of activethermal attenuation control circuits as well as passive thermalattenuation components. Among others, it includes as a first thermalattenuation control circuit a control circuit for specific control ofthe supply temperature of the immersion medium 110.1 to the immersionzone.

To this end, the first thermal attenuation control circuit 112 includesa supply device 112.1, a first temperature adjustment device 112.2,first temperature sensors 112.3 and a control device 111.1. Via at leastone supply line the supply device 112.1 provides the immersion medium110.1 in a sufficient amount and a sufficient flow rate to the immersionzone 110. A first temperature adjustment device 112.2 connected to thecontrol device 111.1 is arranged shortly ahead of the access point ofthe immersion medium 110.1 to the immersion zone 110 and adjusts thetemperature of the immersion medium 110.1 to a desired supplytemperature TIF. The first temperature sensors 112.3 are connected tothe control device 111.1 via wireless and/or at least partially wirebound connections—not shown for reasons of better visibility.

The desired supply temperature TIF is established by the control device111.1 the manner described in the following. the first temperaturesensors 112.3 being evenly distributed at the circumference of theimmersion zone 110 and representing a first establishing device in thesense of the present disclosure the temperature of the immersion medium110.1 at the circumference of the immersion zone 110 is detected. Thefirst temperature sensors 112.3 provide corresponding first temperaturedata to associated inputs 111.2 of the control device 111.1.

However, it will be appreciated that, instead of the direct measurementvia the first temperature sensors 112.3 evenly distributed at thecircumference of the immersion zone 110, a measurement or establishmentof a temperature or at least another parameter may be provided at adifferent location. From this temperature or parameter, in an estimationdevice, via a corresponding sufficiently accurate estimation—based on asufficiently accurately known relation between this establishedparameter and the temperature of the immersion medium 110.1 at thecircumference of the immersion zone 110—the temperature of the immersionmedium at the circumference of the immersion zone 110 may be estimated.

From these first temperature data the control device 111.1 establishesan actual temperature distribution TI within the immersion zone 110using a stored first temperature behavior model of the immersion medium110.1. As further parameters the first temperature behavior model herebyconsiders the actual supply temperature TIF of the immersion medium(provided to the control device 111.1 by the first temperatureadjustment device 112.2), the flow rate of the immersion medium 110.1(provided to the control device 111.1 by the supply device 112.1), theactual temperature distribution TE of the last lens element 109(established in a manner described in further detail below) and theactual light power (provided to the control device by the illuminationdevice 102).

From the actual temperature distribution TI, depending on a givensetpoint temperature distribution TSI within the immersion medium 110.1,the control device 111.1 establishes a first control value C for thetemperature adjustment device 112.2 and/or the supply device 112.1.Using this first control value C the temperature adjustment deviceperforms the adjustment of the supply temperature TIF and/or the supplydevice 112.1 performs adjustment of the flow rate in such a manner thatthe actual temperature distribution TI approaches the setpointtemperature distribution TSI within the immersion medium 110.

Establishment of the supply temperature TIF may be performed as afunction of an alteration ΔTIE within the actual temperaturedistribution TI that is to be expected from the temperatures andparameters previously captured or established. In other words, using thetemperature behavior model, such an alteration ΔTIE may be anticipatedand counteracted prior to its (full) existence.

The actual temperature distribution TI within the immersion medium 110.1represents a parameter P influencing the temperature of the last lenselement 109 since, due to a temperature gradient between the immersionmedium 110.1 and the last lens element 109 a heat transfer occursbetween the immersion medium 110.1 and the last lens element 109 leadingto a temperature alteration in the last lens element 109. Furthermore,the supply temperature TIF and/or the flow rate represent controlparameters since they may be used to influence the temperature gradientbetween the immersion medium 110.1 and the last lens element 109 and theheat transfer between the immersion medium 110.1 and last lens element109, respectively. Accordingly, the temperature adjustment device 112.2and/or the supply device 112.1 respectively represent influencingdevices.

It will be appreciated in this context that the given setpointtemperature distribution TSI within the immersion medium 110.1 may beselected in an arbitrary manner. It may be set in a static manner suchthat, in case of an existence of the setpoint temperature distributionTSI within the immersion medium 110.1 and in case of an existence of thesetpoint temperature distribution TSE within the last lens element 109,no temperature gradient and, consequently, no heat transfer existsbetween the last lens element 109 and the immersion medium 110.

In other words, if the last lens element 109 is in its setpoint state inthis case, no considerable thermal disturbance is introduced into thelast lens element 109 by the immersion medium 110 controlled in thismanner. However, if the last lens element 109 in this case is in a statedeviating from its setpoint state a temperature gradient results betweenthe last lens element 109 and the immersion medium 110.1 counteractingthe actual deviation between the actual temperature distribution TE andthe setpoint temperature distribution TSE of the last lens element 109such that via the immersion medium 110.1 controlled in this manner anattenuation effect is achieved.

The setpoint temperature distribution TSI within the immersion medium110.1 may also be selected as a function of the actual temperaturedistribution TE of the last lens element 109 in such a manner that, incase of an existence of the setpoint temperature distribution TSI withinthe immersion medium 110.1, a given temperature gradient and, thus, agiven heat transfer is provided between the last lens element 109 andthe immersion medium 110.1. The temperature gradient between the lastlens element 109 and the immersion medium 110.1 can be selected in sucha manner that it counteracts a deviation of the actual temperaturedistribution TE of the last lens element 109 from the setpointtemperature distribution TSE of the last lens element 109 such that hereas well a thermal attenuation effect is achieved via the immersionmedium 110.1 controlled in this manner.

In this case the temperature gradient between the last lens element 109and the immersion medium 110.1 set via the immersion medium 110.1 can beselected the higher the higher the deviation of the actual temperaturedistribution TE is from the setpoint temperature distribution TSE of thelast lens element 109. In other words, in this manner a dynamic thermalattenuation of deviations between the actual temperature distribution TEand the setpoint temperature distribution TSE of the last lens element109 may be achieved.

If in this case the last lens element 109 is in its setpoint state theimmersion medium 110.1 controlled in this manner does not introduce aconsiderable thermal disturbance into the last lens element 109. If thisis not the case, the counteraction via the immersion medium 110.1controlled in this manner is the stronger the higher the deviation isbetween the actual temperature distribution TE and the setpointtemperature distribution TSE of the last lens element 109.

The thermal attenuation device 111 further includes as a second thermalattenuation control circuit a control circuit 113 for a specifiedcontrol of the temperature TA and/or the humidity HA and/or the flowrate VA of the gas atmosphere 113.1 contacting the free surface 110.3 ofthe immersion medium 110.1.

The second thermal attenuation control circuit 113, to this end,includes a second supply device 113.2 former gas atmosphere 113.1 andthe control device 111.1. The second supply device 113.2, via at leastone supply line, provides a gas in a sufficient amount where withcorresponding temperature and flow rate at the free surface 110.3 of theimmersion medium 110.1. The second supply device 113.2 adjusts thetemperature and/or the humidity and/or the flow rate of the gasatmosphere 113.12 desired values established by the control device 111.1in the manner described in the following.

The control device 111.1 in the manner described above establishes theactual temperature distribution TI within the immersion medium 110.1within the immersion zone 110. From the actual temperature distributionTI within the immersion medium 110.1 the control device 111.1 thenestablishes, as a function of a given setpoint temperature distributionTSI within the immersion medium, a second control value C for the secondsupply device 113.2. Using the second control value C the second supplydevice 113.2 performs in the adjustment of the temperature and/or thehumidity and/or the flow rate of the gas atmosphere 113.1.

In each case, the adjustment may be provided in such a manner thatevaporation of the immersion medium at the fray surface 110.3 of theimmersion medium 110.1 is minimized. In some embodiments, this happensby adjusting the temperature of the gas atmosphere 113.1 in such amanner that it corresponds to the temperature of the immersion medium110.1 at the free surface 110.3 and by adjusting the humidity of the gasatmosphere 113.1 to a sufficiently high value (e.g., to a completesaturation) in order to avoid evaporation of the immersion medium 110.1and, consequently, a heat transfer from the immersion medium 110.1.

In other words, with this variant, it is avoided that via an evaporationof the immersion medium 110.1 at the free surface 110.3 a thermaldisturbance is introduced into the immersion medium and, thus, also intothe last lens element 109.

The control via the second thermal attenuation control circuit 113 issubordinate to the control via the first thermal attenuation controlcircuit 112. However, in some embodiments, eventually an active use ofthe thermal disturbance via the evaporation induced heat transfer fromthe immersion medium 110.1 may be provided in order to counteractdeviations between the actual temperature distribution TE and thesetpoint temperature distribution TSE of the last lens element 109 and,thus, to achieve a thermal attenuation effect.

For example, in the setpoint state of the last lens element 109, acertain evaporation rate may exist which, depending on the direction ofthe deviation to be attenuated between the actual temperaturedistribution TE and the setpoint temperature distribution TSE of thelast lens element 109, may then be increased or reduced in order toapproach the actual temperature distribution TI of the immersion medium110.1 to a correspondingly changed setpoint temperature distribution TSIof the immersion medium, i.e. to raise or lower, respectively, thetemperature, and, thus to counteract, via the temperature gradientbetween the immersion medium 110.1 and the last lens element 109, thedeviation between the actual temperature distribution TE and thesetpoint temperature distribution TSE of the last lens element 109.

Here as well, the temperature and/or the humidity and/or the flow rateof the gas atmosphere 113.1 represent control parameters CP since, viathese parameters, the temperature gradient between the immersion medium110.1 and the last lens element 109 and the heat transport between theimmersion medium 110.1 and the last lens element 109, respectively, maybe influenced. Accordingly, the second supply device 113.2 alsorepresents an influencing device.

It will be appreciated in this context that, here as well, the givensetpoint temperature distribution TSI within the immersion medium 110.1may be selected arbitrarily in the manner as it has been describedabove. Furthermore, it will be appreciated that the free surface 110.3may be the entire or a part of the free surface of the immersion medium110.1.

The thermal attenuation device 111 further includes as a third thermalattenuation control circuit a control circuit in 114 for a specifieddirect influencing of the temperature of the last lens element 109.

To this end, the third thermal attenuation control circuit 114 includesa plurality of second temperature adjustment devices in the form ofPeltier elements 114.1 evenly distributed at the circumference of thelast lens element 109, second temperature sensors 114.2 and the controldevice 111.1. The Peltier elements 114.1 connected to the control device111.1 cool or heat the last lens element 109—as will be explained in thefollowing in greater detail—in such a manner that a deviation betweenthe actual temperature distribution TE and the setpoint temperaturedistribution TSE of the last lens element is counteracted and, thus, athermal attenuation effect is achieved as well.

Using the second temperature sensors 114.2 and 114.3 evenly distributedat the last lens element 109 and representing a establishment device thetemperature of the last lens element 109 at the respective locations ofthe last lens element 109 is established. The second temperature sensors114.2 and 114.3 provide corresponding first temperature data toassociated inputs 111.2 of the control device 111.1.

It will be appreciated here as well that, instead of the directmeasurement via the temperature sensors 114.2, 114.3 evenly distributedat the last lens element 109, a measure meant or establishment of atemperature or of at least one other parameter may be provided at adifferent location. From this temperature or parameter, in an estimationdevice, via a corresponding sufficiently accurate estimation—based on asufficiently accurately known relation between this establishedparameter and the temperature of the last lens element 109—thetemperature of the last lens element 109 may be estimated.

From these first temperature data the control device 111.1 establishesan actual temperature distribution TE within the last lens element 109using a stored first temperature behavior model of the last lens element109. As further parameters the first temperature behavior model herebyconsiders the actual temperature distribution TI of the immersion medium110.1 and the actual light power (provided to the control device 111.1by the illumination device 102).

From the actual temperature distribution TE within the last lens element109, depending on a given setpoint temperature distribution TSE withinthe last lens element 109, the control device 111.1 establishes a thirdcontrol value C for the Peltier elements 114.1. Using this third controlvalue C the temperature of the surface of the Peltier elements 114.1directed towards the surface of the last lens element 109 is adjusted.Accordingly, Peltier elements 114.1 heat or cool the surface of the lastlens element 109 in such a manner that the actual temperaturedistribution TE approaches the setpoint temperature distribution TSEwithin the last lens element 109.

The temperature of the surface of the Peltier elements 114.1 directedtowards the surface of the last lens element 109 thus represents acontrol parameter CP since, via this temperature the heat transferbetween the Peltier elements 114.1 and the last lens element 109 may beinfluenced. Accordingly, the Peltier elements 114.1 can representinfluencing devices.

As shown in FIG. 3, the third thermal attenuation control circuit 114,with other variants of the microlithography device 101, in addition oras an alternative to the Peltier elements 114.1, may comprise a(further) second temperature adjustment device in the form of aresistance heating device 114.4 in the optically unused area of the lenselement 109. The resistance heating device 114.4 connected to thecontrol device 111.1 heats the last lens element 109—as will beexplained in further detail below—in such a manner that a deviationbetween the actual temperature distribution TE and the setpointtemperature distribution TSE of the last lens element 109 iscounteracted and, thus, a thermal attenuation effect is achieved aswell.

FIG. 3, in a schematic view corresponding to detail D of FIG. 2, shows aresistance heating device 114.4 of a further embodiment of themicrolithography device 101. As may be seen from FIG. 3, the resistanceheating device 114.4 includes a plurality of electrically conductiveelements 114.5 suitably connected to each other and to the controldevice 111.1. The electrically conductive elements 114.5 are embeddedwithin the surface of the last lens element 109.

The electrically conductive elements 114.5 may be fabricated, forexample, by placing a metal powder (later forming the electricallyconductive elements 114.5) on the surface of the last lens element 109in a desired configuration. The metal powder is that heated up, e.g.using a infrared laser, to such an extent that the metal powder meltsand connects to form the electrically conductive elements. Furthermore,due to its higher density, the molten metal powder sinks into thelocally molten matrix of the last lens element 109.

It may be provided that the electrically conductive elements 114.5 are afully embedded within the matrix on the last lens element 109 as it isshown in FIG. 3. In some embodiments, it may also be provided that theelectrically conductive elements 114.5 are only partially surrounded bythe matrix of the last lens element 109. In this case a protective layer(as it is indicated in FIG. 3 by the dashed contour 114.6) may beprovided. This protective layer 114.6 may protect the electricallyconductive elements 114.5 against the aggressive immersion medium 110.1.The protective layer 114.6 may for example be a quartz (SiO) layer thathas been applied via a sputter process, a CVD (chemical vapordeposition) process or the like. It will be further appreciated that theprotective layer 114.6 may eventually comprise the electricalconnections between the electrically conductive elements 114.5 as wellas the electrical connections to the control device 111.1.

As had already been explained, using the second temperature sensors114.2 and 114.3 (see FIG. 2) the temperature of the last lens element109 is captured at the respective locations of the last lens element109. The second temperature sensors 114.2 and 114.3 providecorresponding first temperature data to the associated inputs 111.2 ofthe control device 111.1.

It will be appreciated that, here as well, instead of the directmeasurement via the temperature sensors 114.2, 114.3 evenly distributedover the last lens element 109, a measurement or establishment of atemperature or at least another parameter may be provided at a differentlocation. From this measured or established temperature or parameter, inan estimation device, via a corresponding sufficiently accurateestimation—based on a sufficiently accurately known relation betweenthis established parameter/temperature and the temperature of the lastlens element 109—the temperature of the last lens element 109 may beestimated.

From these first temperature data the control device 111.1 establishesan actual temperature distribution TE within the last lens element 109using a stored first temperature behavior model of the last lens element109. As further parameters the first temperature behavior model herebyconsiders the actual temperature distribution TI of the immersion medium110.1 and the actual light power (provided to the control device 111.1by the illumination device 102).

From the actual temperature distribution TE within the last lens element109, depending on a given setpoint temperature distribution TSE withinthe last lens element 109, the control device 111.1 establishes a thirdcontrol value C for the resistance heating device 114.4. Using thisthird control value C, via a corresponding electric current within theelectrically conductive elements 114.5, the temperature of theresistance heating device 114.4 is adjusted. Accordingly, the resistanceheating device 114.4 heats the last lens element 109 in such a mannerthat the actual temperature distribution TE approaches the setpointtemperature distribution TSE within the last lens element 109.

It will be appreciated that the resistance heating device 114.4 may besegmented in an arbitrarily fine manner, i.e. separated in an arbitrarynumber of segments selectively controllable by the control device 111.1.Using this, it is possible to achieve an arbitrary desired temperaturedistribution within the resistance heating device 114.4.

The temperature of the electrically conductive elements 114.5 thusrepresents a control parameter CP since the heat transfer between theelectrically conductive elements 114.5 and the last lens element 109 maybe influenced by this temperature. Thus, the electrically conductiveelements 114.5 respectively represent an influencing device.

FIG. 4, in a schematic view corresponding to detail D of FIG. 2, shows aresistance heating device 214.4 of a further embodiment of themicrolithography device 101. The resistance heating device 214.4 may beused instead of the resistance heating device 114.4 of FIG. 3. As may beseen from FIG. 4, the resistance heating device 214.4 includes aplurality of electrically conductive elements 214.5 suitably connectedto each other and to the control device 111.1. The electricallyconductive elements 214.5 are arranged on the surface of the last lenselement 109 then and embedded within a protective layer 214.6.

The electrically conductive elements 214.5 may be applied to the surfaceall the last lens element 109 in the desired configuration using a thinlayer technique and/or a thick layer technique. Subsequently, they maybe coated with the protective layer 214.6.

The protective layer 214.6, among others protecting the electricallyconductive elements 214.5 from the aggressive immersion medium 110.1,maybe an arbitrary protective layer. For example, the protective layer214.6 may be a quartz (SiO) layer that has been applied via a sputterprocess, a CVD (chemical vapor deposition) process or the like.

The protective layer 214.6 may also comprise a polymeric material. Apolyimide (PI) material (such as the material sold by DuPont® under thename Kapton®) is particularly suitable. It will be appreciated that, forexample, the protective layer 214.6 may be formed by a polyimide carrierfilm to which the electrically conductive elements 214.5 are applied inthe desired configuration. This carrier film may then be applied to thelast lens element 109 and, for example, the adhesively connected to thelast lens element 109.

As may be seen from FIG. 4, the protective layer 214.6 holds a pluralityof further temperature sensors 214.2 connected to the control device111.1. These temperature sensors 214.2 (in addition or as an alternativeto the temperature sensors 114.2, 114.3) capture the temperature of thelast lens element 109 at the respective location. The temperaturesensors 214.2 provide corresponding first temperature data to theassociated inputs 111.2 of the control device 111.1.

The functionality on the resistance heating device 214.4 is identical tothe functionality of the resistance heating device 114.4 as it has beendescribed above. Thus, it is here only referred to the explanationsgiven above. In particular, the resistance heating device 214.4 againmay be segmented in an arbitrarily fine manner.

FIG. 5, in a schematic view corresponding to detail D of FIG. 2, shows aradiation heating device 314.4 of a further embodiment of themicrolithography device 101. The radiation heating device 314.4 may beused instead of the resistance heating device 114.4 of FIG. 3. As may beseen from FIG. 5 the radiation heating device 314.4 includes a pluralityof heating elements 314.5 connected to the control device 111.1.

The heating elements 314.5 are arranged at the immersion frame 110.2.The heating elements 314.5 under the control of the control device 111.1emit targeted infrared radiation IR towards the last lens element 109 inorder to heat the last lens element 109. The heating elements 314.5 maybe formed by so-called hollow core fibres guiding the infrared radiationof a coupled infrared radiation source of the control device 111.1towards the last lens element 109.

The functionality of the radiation heating device 314.4 largelycorresponds to the functionality of the resistance heating device 114.4as it has been described above. Thus, is here mainly referred to theexplanations given above.

Here as well, from the actual temperature distribution TE within thelast lens element 109, depending on a given setpoint temperaturedistribution TSE within the last lens element 109, the control device111.1 establishes a third control value C for the radiation heatingdevice 314.4. Using this third control value C the radiation intensityof the heating elements 314.5 is adjusted. Accordingly, the heatingelements 314.5 heat the last lens element 109 in such a manner that theactual temperature distribution TE approaches the setpoint temperaturedistribution TSE within the last lens element 109.

The radiation intensity of the heating elements 314.5 thus represents acontrol parameter CP since the heat transfer between the heatingelements 314.5 and the last lens element 109 may be influenced by thisradiation intensity. Thus, the heating elements 314.5 respectivelyrepresent an influencing device.

It will be appreciated that the radiation heating device 314.4 may allowan arbitrarily finely segmented radiation of the last lens element 109.In other words, the radiation heating device 314.4 may comprise anarbitrary number of segments selectively controllable by the controldevice 111.1. Using this, it is possible to provide an arbitraryradiation intensity distribution via the radiation heating device 314.4.

The thermal attenuation control device 111 further includes a firstshielding in the form of a thermally insulating coating 115 of the lastlens element 109, the coating 115 forming a thermal decoupling device inthe form of a first passive thermal attenuation component of theattenuation control device 111.

The coating 115 extends over the section 109.1 of the surface of thelast lens element 109 that it is located adjacent to the immersion ofmedium 110.1 and is optically unused when projecting the projectionpattern onto the wafer 105. Via this thermally insulating coating 115the last lens element 109 and the immersion zone 110 with the immersionmedium 110.1 are section-wise thermally decoupled such that, at leastexternal to the section 109.2 of the surface of the last lens element109 optically used, thermal disturbances in the immersion medium 110.1are prevented from directly propagating within the last lens element109.

The coating 115 may be of any suitable material or material combinationproviding sufficient thermal insulation properties. In the embodimentshown in FIG. 2 the coating 115 includes a layer of an organic material,here a polyurethane (PU) resin, that has been applied to the surfacesection 109.1 of the last lens element 109 via a suitable technique suchas, for example, a casting technique, a varnishing technique etc. Afterits appliance the surface of the organic layer may be treated using anyknown surface treatment technique in order to provide a desired surfaceroughness.

Part or all of the surface of the organic layer not contacting the lastlens element 109 may be provided with a suitable reflective coating.This reflective coating reflects projection light scattered by thesurface of the wafer 105.1 and/or the immersion medium 110.1 and/or theimmersion frame 110.2 etc., thus, preventing (long-term) damage to theorganic layer of the coating 115 that might otherwise be caused by suchscattered projection light.

The shielding 115, in principle, may be designed in any suitable way toprovide the thermal decoupling of the last lens element 109 from itsenvironment, in particular the immersion medium. In particular, it maybe a simple single-layer or multi-layer thermal insulation. As will beexplained in further detail below, it may also be a combination of twoor more layers with at least one highly thermally conductive layer andat least one thermally insulating layer. In this case, the highlythermally conductive layer may serve to transport heat towards thecircumference of the last lens element (to a heat sink eventuallyprovided at this location) and, thus, to prevent or reduce,respectively, its introduction into the last lens element.

In some embodiments, on its side facing away from the last lens element109, the shielding 115 may have a hydrophobic surface. This hydrophobicsurface may eventually be formed by a separate layer only provided forthis reason. Using this, at least largely situations may be avoidedwherein separate drops or droplets of the immersion medium 110accumulate at the (eventually coated) surface of the last lens element109. Such drops or droplets of immersion medium might otherwiseevaporate and cause formation of a locally concentrated strong heat sinkleading to a strong locally concentrated thermal disturbance in the lastlens element 109.

Such drops or droplets of immersion medium 110.1 may for example form atthe surface areas of the last lens element 109 that are only temporarilywetted with the immersion medium 110.1 (e.g. due to wafer movementinduced immersion medium level alterations during operation of themicrolithography device 101). The hydrophobic surface, in anadvantageous manner, hinders formation of such drops or droplets ofimmersion medium 110.1 on the (eventually coated) surface of the lastlens element 109.

FIG. 6, in a schematic view corresponding to detail D of FIG. 2, shows athermal decoupling device in the form of a thermal shielding 415 of afurther embodiment of the microlithography device 101. The shielding 415may be used instead of the shielding 115 of FIG. 2.

As may be seen from FIG. 6, the shielding 415 has a multi-layer designas it has been mentioned above. The shielding 415 includes a combinationof a thermally insulating first layer 415.1 located immediately adjacentto the last lens element 109 and a highly thermally conductive secondlayer 415.2 located immediately adjacent to the first layer 415.1.Furthermore, a hydrophobic third layer 415.3 is applied to the outersurface of the second layer 415.2.

The thermally insulating the first layer 415.1 includes a spacer body415.4. The spacer body 415.4 is of sufficient rigidity to keep its shapeunder any normal operating conditions of the microlithography device101. Thus, the spacer body 415.4, under normal operating conditions,provides a defined distance between the surface of the last lens element109 and the second layer 415.2. In some embodiments, separate spacerelements may be provided instead of a single spacer body.

The spacer body 415.4 is permeable to a fluid (i.e. a gas and/or aliquid). For example, an open-celled foam may be used to form the spacerbody 415.4. Thus, between the surface of the last lens element 109 andthe second layer 415.2, an interstice is defined forming the first layer415.1. The interstice forming the first layer 415.1 is filled with afluid (such as a gas or a liquid) of low thermal conductivity.Eventually, the interstice 415.1 may be (continuously or intermittently)rinsed with a suitably temperature adjusted fluid to guarantee thedesired thermally insulating effect of the first layer 415.1.

In order to prevent ingress of immersion medium 110.1 into theinterstice 415.1 a circumferential sealing element 415.5 is providedbetween the last lens element 109 and the second layer 415.2. Thesealing element 415.5 may be a ring formed by an adhesive which, inaddition, provides fixation on the second layer of 415.2 with respect tothe last lens element 109.

The second layer 415.2, due to its high thermal conductivity, guaranteesa good heat transfer in the radial direction R of the last lens element109. Thus, thermal disturbances induced by the immersion medium 110.1are rapidly reduced or even fully compensated by a correspondingly highheat transfer within the second layer 415.2. Consequently, such thermaldisturbances, if at all, may propagate only to a reduced extent towardsthe last lens element 109. In other words, an efficient thermalattenuation effect is achieved. A further reduction of the propagationof such thermal disturbances is provided by the thermally insulatingfirst layer 415.1. In other words, via the shielding 415 forming athermal decoupling device, the last lens element 109 is effectivelythermally decoupled from its environment, in particular from theimmersion medium 110.1.

In order to achieve a rapid heat transfer within the second layer 415.2a stabilizing device 415.6 may be provided at the outer circumference ofthe second layer 415.2. The stabilizing device may have a high heatcapacity and, thus, a stable temperature during operation of themicrolithography device 101. For example, the stabilizing device 415.6may be formed by a circuit of a heat carrier medium.

The hydrophobic third layer 415.3, again, reduces the likelihood of theformation of local heat sinks due to the evaporation of accumulateddrops or droplets of immersion medium 110.1 as it has been describedabove. The hydrophobic third layer of 415.3 may, for example, be formedby a polyimide (PI) material as it has been mentioned above.

FIG. 7, in a schematic view corresponding to detail D of FIG. 2, shows athermal shielding 515 of a further embodiment of the microlithographydevice 101. The shielding 515 may be used instead of the shielding 115of FIG. 2 or instead of the shielding 415 of FIG. 6.

As may be seen from FIG. 7, the shielding 515 has a multi-layer designas it has been mentioned above. The shielding 515 includes a combinationof a thermally insulating first layer 515.1 located immediately adjacentto the last lens element 109 and a second layer 515.2 locatedimmediately adjacent to the first layer 515.1

The thermally insulating the first layer 515.1 includes a plurality ofspacer elements 515.4 evenly distributed at the circumference of thelast lens element 109. The spacer elements 515.4 are of sufficientrigidity to keep their shape under any normal operating conditions ofthe microlithography device 101. Thus, the spacer elements 515.4, undernormal operating conditions, provide a defined distance between thesurface of the last lens element 109 and the second layer 515.2.

The spacer elements 515.4 define an interstice forming the first layer515.1. The interstice forming the first layer 515.1 is filled with afluid (such as a gas or a liquid) of low thermal conductivity.Eventually, the interstice 515.1 may be (continuously or intermittently)rinsed with a suitably temperature adjusted fluid to guarantee thedesired thermally insulating effect of the first layer 515.1.

In order to prevent ingress of immersion medium 110.1 into theinterstice 515.1 a circumferential sealing element 515.5 is providedbetween the last lens element 109 and the second layer 515.2. Thesealing element 515.5 may be a ring formed by an adhesive which, inaddition, provides fixation on the second layer of 515.2 with respect tothe last lens element 109.

The second layer 515.2 again provides a good heat transfer in the radialdirection R of the last lens element 109. Thus, thermal disturbancesinduced by the immersion medium 110.1 are rapidly reduced or even fullycompensated by a correspondingly high heat transfer within the secondlayer 515.2. Consequently, such thermal disturbances, if at all, maypropagate only to a reduced extent towards the last lens element 109. Inother words, an efficient thermal attenuation effect is achieved. Afurther reduction of the propagation of such thermal disturbances isprovided by the thermally insulating first layer 515.1. In other words,via the shielding 515 forming a thermal decoupling device, the last lenselement 109 is effectively thermally decoupled from its environment, inparticular from the immersion medium 110.1.

The rapid heat transfer within the second layer 515.2 is achieved byproviding a channel system 515.7 extending in the radial direction Rwithin the second layer 515.2. A stabilizing device in the form of apumping and temperature adjusting device 515.6 provides a heat carriermedium circulation with a (e.g., continuous) flow 515.8 of a heatcarrier medium within the channel system 515.7. The heat carrier mediumof the flow 515.8 is adjusted by the stabilizing device 515.6 to have adefined temperature and/or flow rate.

The flow 515.8 initially runs, in a first channel 515.9 of the secondlayer 515.2, in the radial direction R towards a redirecting area 515.10at the inner circumference of the second layer 515.2. At the redirectingarea 515.1 the flow 515.8 is redirected in order to flow back, within asecond channel 515.11 of the second layer 515.2, towards the outercircumference of the second layer 515.2. Leaving the second channel515.11 the flow 515.8 returns to the stabilizing device 515.6 where itis again adjusted in temperature and/or flow rate and re-circulated tothe heat carrier medium circulation.

In the most simple case shown in FIG. 7 the channel system 515.9 to515.11 is formed by a thin hollow body 515.2 and a thin rib 515.12. Therib 515.12 is located within the hollow body 515.2 and extends in theradial direction R and in the circumferential direction of the last lenselement 109. The rib 515.12 separates the first channel 515.9 and thesecond channel 515.11. The second channel 515.11, via which the heatcarrier medium is again transported radially outwards towards thestabilizing device 515.6, can be located on the side facing away fromthe last lens element 109 in order to achieve a rapid removal of thermaldisturbances from the area of the last lens element 109. However, itwill be appreciated that any other suitable configuration of such achannel system providing such a rapid removal of thermal disturbancesmay be used.

Again, a hydrophobic third layer may be provided at the outer surface ofthe second layer 515.2 in order to reduce the likelihood of theformation of local heat sinks due to the evaporation of accumulateddrops or droplets of immersion medium 110.1 as it has been describedabove.

As shown in FIG. 7, the stabilizing device 515.6 may be connected to andcontrolled by the control device 111.1. Thus, it is possible to activelycontrol the thermal attenuation effect on the shielding 515. As aconsequence, the shielding 515 then forms an active thermal decouplingdevice.

In some embodiments, the stabilizing device 515.6 is controlled in sucha manner that a given temperature distribution (e.g., an eventemperature) is substantially maintained (throughout the operation ofthe microlithography device 101) at the surface of the second layer515.2 (forming a thermal shielding element) facing the last lens element109. To this end, further temperature sensors 514.2 connected to thecontrol device 111.1 may be provided at this surface. The control device111.1 may then use the temperature data provided by the temperaturesensors 514.2 to control the stabilizing device 515.6 in the mannerdescribed above.

FIG. 8, in a schematic view corresponding to detail D of FIG. 2, shows athermal shielding 615 of a further embodiment of the microlithographydevice 101. The shielding 615 may be used instead of the shielding 115of FIG. 2, instead of the shielding 415 of FIG. 6 or instead of theshielding 515 of FIG. 7.

As may be seen from FIG. 8, the shielding 615 is formed by a (e.g.,continuous) flow 615.13 of a heat carrier medium 615.14 provided withinthe part 110.4 of the gap between the last lens element 109 and theimmersion frame 110.2 that is not filled with the immersion medium110.1. The flow 615.13 is provided by a stabilizing device in the formof a pumping and temperature adjusting device 615.6 that provides theheat carrier medium with a defined temperature and flow rate.

The flow 615.13 initially runs in the radial direction R towards acontact zone 615.14. Within this contact zone 615.15 the heat carriermedium 615.14 contacts and eventually mixes with the immersion medium110.1. In the area of the contact zone 615.5 a channel 615.16 isprovided within the immersion frame 110.2. The channel 615.16 openstowards the contact zone 615.5. Via this channel 615.16 the heat carriermedium 615.14 and, eventually, part of the immersion medium 110.1(eventually mixed with the heat carrier medium 615.14) are drawn offfrom the gap between the last lens element 109 and the immersion frame110.2 and re-circulated back to the stabilizing device 615.6.

In the stabilizing device 615.6, if necessary, the fraction of theimmersion medium 110.1 drawn off together with the heat carrier medium615.14 is separated from the heat carrier medium 615.14. The stabilizingdevice 615.6 re-adjusts the temperature and flow rate of the heatcarrier medium 615.4 and re-circulates to the heat carrier mediumcirculation.

The stabilizing device 615.6 also provides the immersion medium 110.1 tothe immersion zone 110 at the desired flow rate. It will be appreciatedthat the flow rate of the immersion medium 110.1 provided to theimmersion zone 110 and the flow rate of the heat carrier medium 615.14provided to the part 110.4 of the gap between the last lens element 109and the immersion frame 110.2 as well as the flow rate within thechannel 615.16 are mutually adapted to each other in order to achievethe configuration as described above (i.e. with the immersion medium110.1 and the heat carrier medium 615.14 contacting in the contact zone615.15). Furthermore, these flow rates are mutually to adapted eachother in order to avoid undesired pressure fluctuations within the areaof the last lens element 109.

The flow 615.13 provides a good heat transport away from the last lenselement 109 in the radial direction R of the last lens element 109.Thus, thermal disturbances induced by the immersion medium 110.1 or theimmersion frame 110.2 are rapidly reduced or even fully compensated by acorrespondingly high heat transport provided by the flow 615.13.Consequently, such thermal disturbances, if at all, may propagate onlyto a reduced extent towards the last lens element 109. In other words,an efficient thermal attenuation effect is achieved. A further reductionof the propagation of such thermal disturbances may be provided by athermally insulating first layer on the last lens element as it isindicated by the dashed contour 615.1 in FIG. 8. In other words, via theshielding 615 forming a thermal decoupling device, the last lens element109 is effectively thermally decoupled from its environment, inparticular from the immersion medium 110.1.

As shown in FIG. 8, the stabilizing device 615.6 may be connected to andcontrolled by the control device 111.1. Thus, it is possible to activelycontrol the thermal attenuation effect on the shielding 615.

The thermal attenuation device 111 further includes a ring shaped secondshielding 116 arranged between the holder 117 of the last lens element109 and the holder of 118 on the penultimate lens element 108 andforming a second passive thermal attenuation component and, thus, athermal decoupling device.

The second shielding 116 extends from the connection area of the twoholders 117 and 118 (to the housing of the objective 104) up to thesection 109.3 on the surface of the last lens element 109 that isoptically unused during projecting the projection pattern onto the wafer105. The second shielding 116 further serves as the carrier for thePeltier elements 114.1.

The second shielding 116 as shown in FIG. 8 includes a highly thermallyconductive material. In the connection area of the two holders 117 and118 the second shielding 116 is connected to a temperature-stabilizedintermediate element 119 which is, via a ring channel 119.1, passedthrough with a heat carrier medium, e.g. water, that is held at aconstant temperature via a heat carrier medium source 119.2.

Using a constant temperature of the temperature-stabilized intermediateelement 119 and the high thermal conductivity of the second shielding116 an approximately constant temperature results on the side of thesecond shielding 116 facing towards the holder 117. Accordingly, athermal shielding of the holder of 117 and of a part of the last lenselement 109 from the rest of the objective 104 is achieved such that,here as well, an attenuation of thermal disturbances of the last lenselement 109 introduced via this side is achieved.

it will be appreciated that, in principle, the second shielding 116again may be designed in any suitable way. In some embodiments, it mayalso be designed as a simple single-layer or multi-layer thermalinsulation similar to the variants of the first shielding describedabove. However, it may also be a combination of two or more layerscomprising at least one highly thermally conductive layer and at leastone thermally insulating layer. In particular, in the embodiment shownin FIG. 8, a correspondingly insulating layer may be formed on the sideof the second shielding 116 facing the holder 117.

FIG. 9 shows a block diagram of an embodiment of the optical imagingmethod which may be executed with the microlithography device 101.

First, in a step 120.1 execution of the method starts. In a step 120.2the components of the microlithography device 101 are mutuallypositioned with respect to each other such that the configurationdescribed above is achieved.

In a step 120.3 at least a part of the projection pattern on the mask103.1 is projected onto the wafer 105.1 in the matter as it has beendescribed above. In the step 120.3, in parallel to this projection, athermal attenuation of fluctuations in the temperature distribution ofthe last lens element 109 induced by the environment of the last lenselement, in particular by the immersion medium 110.1, is provided viathe thermal attenuation device 111 as it has been described above.

To this end, in a step 120.4, the corresponding temperatures areestablished via the temperature sensors 112.2, 112.3, 114.2, 114.3 as ithas been described above. Furthermore, further parameters such as theactual supply temperature TIF of the immersion medium 110.1, the flowrate of the immersion medium 110.1 and the actual light power of theillumination device 102 are established as it has been described above.

In a step 120.5 the control device 111 establishes the actualtemperature distribution TI within the immersion medium 110.1 in theimmersion zone 110 as well as the actual temperature distribution TE ofthe last lens element 109. This is done using the stored temperaturebehavior model and using the data established in step 120.3 as it hasbeen described above. Furthermore, the control device 111 establishesthe control values C for the separate influencing devices (e.g.temperature adjustment device 112.2, supply device 112.1, second supplydevice 113.2, Peltier elements 114.1 etc.).

The temperature behavior model hereby represents the relation betweenthe captured or otherwise established temperatures as well as furtherparameters (e.g. flow rate of the immersion medium 110.1, light power ofthe illumination device 102 etc) and the temperature distribution to beexpected within the respective object of the temperature behavior model(i.e. the last lens element 109 and the immersion medium 110.1,respectively).

The respective part of the temperature behavior model may have beenestablished for the respective object of the temperature behavior model(i.e. the last lens element 109 or the immersion medium 110.1) in anempiric manner and/or via simulation calculations. In particular forregularly repeated situations during operation of the microlithographydevice 101 a sufficiently accurate estimation of the actual temperaturedistribution TI within the immersion medium 110.1 in the immersion zone110 as well as of the actual temperature distribution TE within the lastlens element 109 May be achieved.

In a step 120.6, using the established control values C, the controlparameters CP are influenced by controlling the respective influencingdevices (e.g. temperature adjustment device 112.2, supply device 112.1,second supply device 113.2, Peltier elements 114.1 etc.) via the controldevice 111.1 in the manner as it has been described above.

In a step 120.7 it is checked if execution of the method is to bestopped. If this is the case, execution of the method is stopped in astep 120.8. Otherwise it is jumped back to step 120.3.

In the foregoing, embodiments have been described using an example wherea plurality of active thermal attenuation control circuits 112, 113, 114and passive thermal attenuation components 115, 116 are provided incombination. In some embodiments, the single active thermal attenuationcontrol circuits and passive thermal attenuation components may each beused alone or in an arbitrary combination.

Furthermore, while in the foregoing examples, a part of the last lenselement 109 is immersed in an immersion medium 110.1 during opticalimaging, embodiments may also be used in the context of immersionsystems wherein an immersion zone at least temporarily filled with animmersion medium (in addition or as an alternative to the immersion zonebetween the last lens element and the wafer) is located between twooptical elements of the optical element group. Such multiple immersionsystems or double immersion systems are known for example from WO2006/080212 A1, WO 2004/019128 A2, WO 2006/051689 A1, WO 2006/126522 A1,WO 2006/121008 A1 and U.S. Pat. No. 7,180,572 B1, the entire disclosureof all of which is included herein by reference.

FIG. 10, in a view corresponding to the view of FIG. 2, schematicallyshows such a double immersion system which may be used in themicrolithography device 101. Here, the lens element 109 is not locatedimmediately adjacent to the wafer 105.1 but adjacent to a furtheroptical element in the form of a lens element 709 located between thelens element 109 and the wafer 105.1. The immersion zone 110 is locatedbetween the lens element 109 and the lens element 709 while a furtherimmersion zone 710 filled with a further immersion medium 710.1 islocated between the further lens element 709 and the wafer 105.1.

The thermal attenuation device 111 is configured in a manner as it hasbeen described above in order to provide thermal attenuation ofenvironment induced thermal disturbances tending to cause thermaldisturbances within the temperature distribution of the lens element109. It will be appreciated that a further thermal attenuation devicemay be provided to provide thermal attenuation of environment induced,in particular immersion medium induced thermal disturbances tending tocause thermal disturbances within the temperature distribution of thefurther lens element 709. This further thermal attenuation device may bedesigned in a manner similar to the thermal attenuation device 111.Furthermore, the thermal attenuation device 111 may also be designed toprovide such thermal attenuation for the further lens element 709.

The immersion medium 110.1 may be identical with or different from theimmersion medium 610.1. Any suitable immersion medium may be used.Examples of such immersion media are heavy water or heavy oxygen watersuch as D₂O, D₂O*, H₂O*, wherein O* may comprise the isotopes O¹⁶, O¹⁷and O¹⁸. These immersion media may be mixed in an arbitrary ratio inorder to achieve a desired refractive index in the respective immersionzone 110 and 710, respectively, and/or in order to achieve a desiredrelation between the refractive indices of the two immersion mediaand/or a desired relation between the refractive indices of the opticalelements 109, 709 and one or both of the immersion media 110.1, 710.1.Corresponding examples and values of refractive indices for suchmixtures are given in US 2006/092533 A1, US 2006/066926 A1 and WO2005/106589 A1, the entire disclosure of each of which is incorporatedherein by reference.

While examples are described wherein the optical element group iscomposed of refractive optical elements exclusively, in someembodiments, optical element groups that include, alone or in anarbitrary combination, refractive, reflective or diffractive opticalelements can be used, in particular in the case of performing theimaging process at different wavelengths.

Furthermore, while embodiments have been described in relation tomicrolithography, other applications (e.g., imaging processes) are alsopossible. Other embodiments are in the following claims.

1. (canceled)
 2. An optical imaging device, comprising: a mask deviceconfigured to receive a mask comprising a pattern; a substrate deviceconfigured to receive a substrate; a projection device comprising anoptical element group configured to project the pattern onto thesubstrate, the projection device comprising a plurality of opticalelements which comprise an immersion element; and a thermal attenuationdevice comprising an influencing device, wherein: the optical imagingdevice comprises an immersion zone between the immersion element and thesubstrate; during use of the optical imaging device: the immersionelement is at least temporarily located adjacent to the immersion zone;and the immersion zone at least temporarily contains an immersionmedium; the thermal attenuation device reduces fluctuations within atemperature distribution of the immersion element induced by theimmersion medium; and as a function of at least one control value, theinfluencing device influences the temperature distribution of theimmersion element induced by the immersion medium.
 3. The opticalimaging device of claim 2, further comprising a holding device holdingthe immersion element, wherein: the thermal decoupling device comprisesa first shielding, a second shielding and a third shielding; during useof the optical imaging device: the immersion element comprises a firstarea which optically used and a second area which optically unused; thefirst shielding thermally shields at least a part of a first section ofthe second area against the immersion medium, the first section being anentire section of the second area located adjacent to the immersionmedium; the second shielding thermally shields at least a part of asecond section of the second area against an adjacent section of theprojection device, the second section being an entire section of thesecond area located adjacent to the adjacent section of the projectiondevice; and the third shielding thermally shields at least a part of theholding device against its environment.
 4. The optical imaging device ofclaim 2, further comprising a thermal decoupling device, wherein atleast one of the following holds: the thermal decoupling device isconfigured to at least partially thermally decouple the immersionelement from at least a part of its environment; the thermal decouplingdevice comprises a passive thermally insulating device; the thermaldecoupling device comprises an organic material; the thermal decouplingdevice comprises an active shielding comprising a shielding element anda temperature adjustment device connected to the shielding element, thetemperature adjustment device configured to maintain a selectabletemperature distribution on a surface of the shielding element; thethermal decoupling device comprises an active shielding, the temperatureadjustment device configured to provide a flow of a heat carrier mediumin an area of the active shielding element; and the thermal decouplingdevice comprises a hydrophobic surface facing away from the immersionelement; the thermal decoupling device comprises a hydrophobic coatingfacing away from the immersion element.
 5. The optical imaging device ofclaim 2, wherein the thermal attenuation device is configured tomaintain a maximum deviation from a setpoint temperature distributionfor the immersion element.
 6. The optical imaging device of claim 5,wherein the maximum deviation is less than 10 milliKelvin.
 7. Theoptical imaging device of claim 2, wherein: the immersion element has anactual temperature distribution; the immersion medium has a setpointtemperature distribution; the thermal attenuation device furthercomprises an establishing device and a control device; the controldevice is at least temporarily connected to both the establishing deviceand the influencing device; the establishing device establishes aparameter that influences the actual temperature distribution or that isrepresentative of the actual temperature distribution; the controldevice is configured to establish the control value as a function of theparameter and the setpoint temperature distribution; the influencingdevice is configured to influence a control parameter as a function ofthe at least one established control value; and the control parameterinfluences the actual temperature distribution to counteract a deviationof the actual temperature distribution from the setpoint temperaturedistribution.
 8. The optical imaging device of claim 7, wherein theparameter comprises a parameter selected from the group consisting of alocal temperature of the immersion medium and a local temperature of theimmersion element.
 9. The optical imaging device of claim 8, wherein theestablishing device comprises a device configured to: a) measure thelocal temperature; and/or b) estimate the local temperature.
 10. Theoptical imaging device of claim 7, wherein the control parameter isselected from the group consisting of a temperature of the immersionmedium, a flow rate of the immersion medium, a temperature of a gasatmosphere contacting the immersion medium, a humidity of a gasatmosphere contacting the immersion medium, a flow rate of a gasatmosphere contacting the immersion medium, and a temperature of antemperature adjustment element operatively connected to the immersionelement.
 11. The optical imaging device of claim 2, further comprising acontrol device configured to use a model to establish the control value,the model comprising a model selected from the group consisting of atemperature behavior model of the immersion element and a temperaturebehavior model of the immersion medium within the immersion zone forestablishing the control value.
 12. The optical imaging device accordingclaim 11, wherein: the control device comprises a memory to store datarepresenting the model or parameters to calculate model datarepresenting the model; and during use of the optical imaging device,the control device uses the model data to establish the control value.13. The optical imaging device of claim 2, wherein the influencingdevice comprises a temperature adjustment device configured to adjustthe temperature of the immersion medium during use of the opticalimaging device.
 14. The optical imaging device of claim 13, furthercomprising a control device, wherein during use of the optical imagingdevice: the control device establishes the control value for thetemperature adjustment device as a function of an alteration of atemperature distribution expected within the immersion medium so thatthe temperature adjustment device adjusts the temperature of theimmersion medium supplied to the immersion zone to a supply temperature;and the supply temperature is selected so that, due to the alteration ofthe temperature distribution to be expected within the immersion medium,a given temperature distribution is to be expected within the immersionmedium.
 15. The optical imaging device of claim 13, wherein thetemperature adjustment device is arranged in an area of an inlet of theimmersion medium to the immersion zone.
 16. The optical imaging deviceof claim 2, wherein the influencing device comprises an adjustmentdevice configured to influence evaporation induced cooling of theimmersion medium in a contact area with an adjacent gas atmosphere, theadjustment device is configured to adjust at least one parameterselected from the group consisting of a temperature of the gasatmosphere, a humidity HA of the gas atmosphere, and a flow rate VA ofthe gas atmosphere.
 17. The optical imaging device of claim 16, furthercomprising a control device configured to establish the control valuefor the adjustment device as a function of a state of the immersionmedium in the contact area to provide a given evaporation inducedcooling of the immersion medium in the contact area or substantially noevaporation induced cooling of the immersion medium in the contact area.18. The optical imaging device of claim 16, wherein the contact areasubstantially extends over an entire free surface of the immersionmedium.
 19. The optical imaging device of claim 2, wherein theinfluencing device comprises a first temperature adjustment device, asecond temperature adjustment device, a third temperature adjustmentdevice and a fourth temperature adjustment device, wherein: thetemperature adjustment device defines the influencing device inoperative connection with the immersion element to adjust a temperatureof the immersion element; the first temperature adjustment device is inan area of a circumference of the immersion element; the secondtemperature adjustment device comprises a Peltier-Element; the thirdtemperature adjustment device comprises a resistance heating devicewhich is arranged at the immersion element, embedded within theimmersion element and/or covered with a protection layer against theimmersion medium; the fourth temperature adjustment device comprises aradiation heating device to provide heating radiation to the immersionelement or infrared radiation to the immersion element.
 20. The opticalimaging device of claim 19, further comprising a control deviceconfigured to establish the control value for the temperature adjustmentdevice defining the influencing device as a function of a temperaturedistribution within the immersion medium in the immersion zoneestablished by the establishing device so that the temperatureadjustment device adjusts the temperature of the immersion element tocounteract a deviation of the actual temperature distribution from asetpoint temperature distribution that is due to the establishedtemperature distribution within the immersion medium.
 21. The opticalimaging device of claim 2, wherein during use of the optical imagingdevice: the immersion element has an actual temperature distribution anda setpoint temperature distribution is given for the immersion element;the setpoint temperature distribution is selected to achieve an imagingerror influence comprising a reduction of an imaging error of theimmersion element, a minimization of an imaging error of the immersionelement, a reduction of an imaging error of the optical element group,and/or a minimization of an imaging error of the optical element group.22. The optical imaging device of claim 2, wherein the immersion elementcomprises a first material, a second material, a third material and afourth material, wherein: the first material has a refractive indexlarger than a refractive index of quartz glass; the second material hasa refractive index with a higher temperature sensitivity than arefractive index of quartz glass; the third material comprises a spinelmaterial; and the fourth material comprises a LuAG material.
 23. Theoptical imaging device of claims 2, wherein the immersion elementcomprises a last optical element of the optical element group at leasttemporarily located adjacent to the substrate during use of the opticalimaging device.
 24. A device, comprising: an illumination system; andthe optical imaging device of claim 2, wherein the device is amicrolithography device.
 25. A method of using a microlithography devicecomprising an illumination system and an optical imaging device, themethod comprising: using optical elements of the optical imaging deviceto project a pattern onto a substrate, wherein the optical imagingdevice is an optical imaging device according to claim
 2. 26. A methodof using an optical element group comprising optical elements includingan immersion element, the method comprising: a) using the opticalelement group to project a pattern of a mask onto a substrate while theimmersion element contacts an immersion medium disposed between theimmersion element and the substrate; and b) during a), using a thermalattenuation device to reduce fluctuations in a temperature distributionof the immersion element induced by the immersion medium as a functionof a control value.
 27. The method of claim 26, wherein: at least one ofa first thermal decoupling, a second thermal decoupling, and a thirdthermal decoupling is provided, each decoupling providing at leastpartial thermal decoupling of the immersion element from at least a partof its environment; the first thermal decoupling comprises a passivethermally insulating device and/or an organic material; the secondthermal decoupling comprises an active shielding comprising a shieldingelement and a temperature adjustment device connected to the shieldingelement, the temperature adjustment device is arranged so that aselectable temperature distribution on at least one surface of theshielding element is substantially maintained; and the third thermaldecoupling being provided via at least one active shielding having atleast one shielding element and at least one temperature adjustmentdevice connected to the shielding element, the temperature adjustmentdevice providing a flow of a heat carrier medium in the area of the atleast one shielding element.
 28. The method of claim 26, furthercomprising providing a setpoint temperature distribution for theimmersion element, and using the thermal attenuation device to maintaina given maximum deviation from the setpoint temperature distribution.29. The method of claim 26, wherein: the last immersion element has anactual temperature distribution and a setpoint temperature distributionis given for the immersion element; establishing a parameter thatinfluences the actual temperature distribution or a representative ofthe actual temperature distribution; establishing a control value as afunction of the established parameter and the setpoint temperaturedistribution; and as a function of the control value, influencing acontrol parameter that influences the actual temperature distribution tocounteract a deviation of the actual temperature distribution from thesetpoint temperature distribution.
 30. The method of claim 29, whereinthe parameter a measured local temperature of the immersion medium, anestimated local temperature of the immersion medium, a measured localtemperature of the immersion element, and/or an estimated localtemperature of the immersion element.
 31. The method of claim 26,further comprising using a model to establish the control value, whereinthe model comprises a temperature behavior model of the immersionelement, and/or a temperature behavior model of the immersion mediumwithin the immersion zone.
 32. The method of claim 26, furthercomprising: adjusting a temperature of the immersion medium supplied tothe immersion zone; and establishing the control value as a function ofan alteration the temperature distribution to be expected within theimmersion medium to adjust the temperature of the immersion mediumsupplied to the immersion zone to a supply temperature, wherein thesupply temperature TIF is selected such that, due to the alteration ofthe temperature distribution to be expected within the immersion medium,a given temperature distribution is to be expected within the immersionmedium.
 33. The method of claim 26, wherein: using the thermalattenuation device to influence evaporation induced cooling of theimmersion medium in a contact area with an adjacent gas atmosphere;adjusting a state parameter of the gas atmosphere contacting theimmersion medium is adjusted; and establishing the control value as afunction of the state of the immersion medium in the contact area sothat a given evaporation induced cooling of the immersion medium is tobe expected in the contact area, or substantially no evaporation inducedcooling of the immersion medium is to be expected in the contact area.34. The method of claim 26, further comprising directly adjusting atemperature of the immersion element, and establishing the control valueas a function of a temperature distribution within the immersion mediumin the immersion zone so that the temperature of the immersion elementis adjusted to counteract a deviation of the actual temperaturedistribution from the setpoint temperature distribution that is due tothe established temperature distribution within the immersion medium.35. The method of claim 26, wherein: the immersion element has an actualtemperature distribution TE and a setpoint temperature distribution TSEis given for the immersion element; and the setpoint temperaturedistribution TSE is selected to reduce and/or minimize an imaging errorof the immersion element and/or the optical element group.